# A knight and a thief walk into a bar and meet three gods……

Most people have heard the logic puzzle about the knight and the thief. The knight always tells the truth and the thief always lies. If you happen to run into the two of them on the road one day, how can you figure out who is whom by asking just one yes-or-no question?

A solution is to ask either of them if the other would claim to be the knight. If he answers no, then he is a knight because the thief would lie and say that he is not a knight, but because he does not lie he will truthfully report what the thief will say, which is no. On the other hand if the person you ask says yes, then you can deduce that he is a thief because the knight will truthfully reply that the person you asked is not a knight, but because as a thief he will always lie he will report the opposite of what the knight says, which is yes. Of course there are many ways to solve this puzzle, including the use of counterfactuals. For example, you could ask one of them, “If I were to ask if you are a knight, would you say yes?” A yes response in this case would mean that the person is a knight and a no would mean that he is a thief.